Apolipoprotein E and neurocognitive outcome from coronary artery surgery

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Abstract
The apolipoprotein E (apoE) gene (APOE) is polymorphic with three alleles, ε2, ε3, and ε4, which give rise to three isoforms, E2, E3 and E4. Many reports have now described a strong association between the ε4 allele and risk of developing late onset Alzheimer's disease as the result of the E4 isoform binding to β-amyloid protein and accelerating the deposition of amyloid, which is the main constituent of senile plaques.1 The APOE ε4 allele also appears to be associated with deposition of β-amyloid after traumatic brain injury, which is also accompanied by increased APOE expression in the central and peripheral nervous systems. Neurological and cognitive decrements are well documented complications of coronary artery bypass grafting (CABG) surgery. Given that APOE ε4 is associated with deposition of β-amyloid after traumatic brain injury, and poor neurological outcome after subarachnoid haemorrhage and stroke, it may also adversely influence neurocognitive outcome after CABG surgery. In a preliminary report, Tardiff and colleagues2 found that the APOE ε4 allele was associated with greater risk of cognitive impairment, especially in those patients with lower educational levels. More recently, Steed and colleagues3 were unable to replicate the findings in …